Plasma processing chambers can include an upper electrode and a lower electrode. The upper electrode typically faces a substrate support adapted to support a semiconductor substrate during plasma processing. During the plasma processing, power is supplied to one or both electrodes to activate the process gas and produce the plasma to process the substrate.
Plasma etching can be performed in plasma processing chambers to etch selected materials provided as layers on a semiconductor substrate. The processing conditions are chosen so that the plasma etches desired features in the layers.
As described in commonly-assigned U.S. Pat. No. 7,430,986, during plasma etching in parallel plate capacitively coupled plasma chambers with highly polymerizing process gas chemistries, polymer deposits can form on internal chamber surfaces such as plasma confinement rings. The rings move vertically and as described in commonly-owned U.S. Pat. No. 6,936,135, during wafer processing the confinement rings may be brought closer together with the bottom ring adjacent the substrate support. The vertical movement creates opportunity for moving parts to scrape against each other and generate particles which can cause particle contamination of the processed wafer. Improvements in plasma confinement arrangements which reduce particle generation would be desirable.